Methods of fabricating a semiconductor device using a dilute aqueous solution of an ammonia and peroxide mixture

ABSTRACT

This invention provides methods of fabricating semiconductor devices, wherein an alloy layer is formed on a semiconductor substrate to form a substrate structure, which methods include using an aqueous solution diluted ammonia and peroxide mixture (APM) to perform cleaning and/or wet etching treatment steps on the substrate structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.11/089,208, filed on Mar. 24, 2005, which relies for priority uponKorean Patent Application No. 10-2004-0020521, filed Mar. 25, 2004, thecontents of which are hereby incorporated by reference in theirentirety.

BACKGROUND OF INVENTION

1. Technical Field

The present invention relates generally to methods of fabricating asemiconductor device, and more particularly, to methods of fabricating asemiconductor device using a dilute aqueous solution of an ammonia andperoxide mixture (hereinafter abbreviated as “APM”).

2. Discussion of the Related Art

Recently, semiconductor fabrication processes have focused on forming atransistor on a silicon-germanium layer (rather than on a substantiallyhomogeneous single crystalline silicon substrate) in order to meetgrowing market demand for semiconductor devices having properties ofhigher speed and a higher degree of integration. The silicon-germaniumlayer is typically formed by applying germanium atoms to a surface of asingle crystalline silicon substrate to form a silicon-germanium alloythereon.

Using a silicon-germanium (SiGe) layer in semiconductor fabricationincreases the mobility of a carrier by using a lattice constantdifferent from the single crystalline silicon substrate conventionallyused in semiconductor devices. The increase in the mobility of thecarrier results in improving a current driving capability of thetransistor. This gives a breakthrough for relatively easily improvingthe speed of a transistor of any given size rather than improving thespeed by arbitrarily reducing a size thereof. The lattice constant ofthe silicon-germanium (SiGe) layer has been found to be proportional tothe amount of germanium atoms contained in the SiGe layer.

However, the silicon-germanium layer has the disadvantageous property ofbeing vulnerable to an aqueous solution containing ammonium hydroxideand hydrogen peroxide. This is because the silicon-germanium layerreadily reacts with hydrogen peroxide (H₂O₂) to first form a siliconoxide layer, and that silicon oxide layer is then excessively etched bythe ammonium hydroxide. Such an excessively etched silicon-germaniumlayer significantly impairs the performance characteristics of theresulting transistor.

U.S. Pat. No. 6,399,487 to Jane-Bai Lai, et. al (the '487 patent), whichis incorporated herein by reference, discloses a method of reducingphase transition temperature by using silicon-germanium alloys.

According to the '487 patent, the method includes forming a gate of apolysilicon layer on a silicon substrate and forming a silicon-germaniumalloy layer on the gate. Thereafter, a titanium layer is formed on thesilicon-germanium alloy layer through a salicide process, along withforming source and drain regions overlapping the gate. The '487 patentfurther teaches that the titanium forms a titanium alloy wherever thetitanium is in contact with the silicon-germanium alloy, but thatunreacted titanium may subsequently be removed from the siliconsubstrate by an etching step using an aqueous solution of ammonia andhydrogen peroxide “which results in removal of all unreacted titanium,leaving behind conductive material over the source, drain, and gate butnot over the spacers.”

However, the aqueous solution of ammonia and hydrogen peroxide used inthis step may excessively etch the upper surface and the sidewalls ofthe silicon-germanium alloy unless the volume ratios of ammonia andhydrogen peroxide in the aqueous solution are optimized and contact timeis carefully controlled.

These and other problems with and limitations of the prior artapproaches to fabricating semiconductor devices which include asilicon-germanium layer are addressed in whole or at least in part bythe methods of this invention.

SUMMARY OF THE INVENTION

According to some embodiments of the present invention, there areprovided methods of fabricating a semiconductor device capable ofoptimizing a physical property of a surface of a (Si_(1−x)Ge_(x)) alloylayer by using a dilute aqueous solution consisting essentially of anammonia and peroxide mixture (APM), where “x” is a fraction or a decimalhaving a value greater than 0 but less than 1.

According to some embodiments of the present invention, there areprovided methods of fabricating a semiconductor device by performing apost-cleaning process on a fabricated structure having at least one pairof elements consisting of a first material layer and a second(Si_(1−x)Ge_(x)) alloy layer using a dilute aqueous solution consistingessentially of an ammonia and peroxide mixture in order to obtain adesirable profile of the different layers.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be readily apparent to thoseof ordinary skill in the art upon review of the detailed descriptionthat follows when taken in conjunction with the accompanying drawings,in which like reference numerals denote like parts. In the drawings:

FIGS. 1 through 5 are schematic cross-sectional views of portions ofsemiconductor devices illustrating a method of forming a trench in asubstrate having a silicon germanium alloy layer and another materiallayer according to an embodiment of the invention, respectively;

FIG. 6 is a schematic cross-sectional view of a portion of asemiconductor device showing a bar pattern having at least one pair ofelements consisting of a silicon-germanium alloy layer and anothermaterial layer on a substrate according to an embodiment of theinvention;

FIGS. 7 and 8 are graphs showing etching ratios of aqueous solutionscontaining different proportions of ammonium hydroxide, hydrogenperoxide, and water respectively;

FIGS. 9 through 14 are schematic cross-sectional views of portions ofsemiconductor devices treated by using various aqueous solutionsconsisting essentially of ammonium hydroxide and hydrogen peroxide,respectively;

FIG. 15 is a schematic cross-sectional view of a semiconductor devicehaving a silicon-germanium alloy layer according to an embodiment of theinvention; and

FIG. 16 is a graph showing comparative surface roughnesses of differentalloy layers either left untreated or treated using aqueous solutionsconsisting essentially of ammonium hydroxide and hydrogen peroxide.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 5 are schematic cross-sectional views of portions ofsemiconductor devices illustrating a method of forming a trench in asubstrate having a silicon-germanium alloy layer and another materiallayer according to an embodiment of the invention, respectively.

Referring to FIGS. 1 through 5, an alloy layer 20 and a material layer30 are sequentially formed on a suitable semiconductor substrate 10. Thematerial layer 30 may be formed, for example, of a strained siliconlayer by using an epitaxial process. The alloy layer 20 is formed of asilicon-germanium (Si_(1−x)Ge_(x)) alloy layer such that germanium atomsare present in alloy layer 20 in the range of greater than 0 to about99% by atomic weight with respect to the presence of silicon atoms. Thealloy layer 20 having suitable proportions of silicon and germanium maybe formed, for example, by using a chemical vapor deposition process.The substrate 10 is preferably formed of a single crystalline siliconlayer, but may, in some invention embodiments, be formed of apolycrystalline silicon layer.

A mask layer 40 and a photoresist layer 50 are then sequentially formedon the material layer 30, as shown in FIG. 2, and a photolithographyprocess is thereafter performed in the photoresist layer 50 to formphotoresist patterns 55 (as shown in FIG. 3) on the mask layer 40. Usingthe photoresist patterns 55 as an etching mask, an etching process isnext performed in the mask layer 40 to form mask patterns 45 between thematerial layer 30 and the photoresist patterns 55 as shown in FIG. 3.The etching process is preferably performed by using a dry etchingtechnique.

The photoresist patterns 55 are then removed from the semiconductorstructure using conventional techniques. Using the mask patterns 45 asan etching mask, an etching process is then sequentially performed inthe material layer 30, the alloy layer 20 and the substrate 10. Theetching process is preferably performed by using a dry etchingtechnique. This etching process results in penetrating the materiallayer 30 and the alloy layer 20 in order to form a trench 60 thatextends in part into the substrate 10. This etching process also resultsin exposing a sectional surface of the alloy layer 20 adjoining thetrench 60 as shown in FIG. 4. Then, the mask patterns 45 are removedfrom the semiconductor structure using conventional techniques.

In accordance with this invention, a post-cleaning process may now beperformed on the structure to remove by-products such as organicparticles and polymer from the substrate having the trench 60. Thepost-cleaning process is performed in accordance with this invention byusing an aqueous solution consisting essentially of ammonium hydroxide(NH₄OH), hydrogen peroxide (H₂O₂), and deionized water (DI-water).

FIG. 6 is a schematic cross-sectional view of a semiconductor deviceshowing a bar pattern having at least one pair of elements consisting ofa silicon-germanium alloy layer and another material layer on asubstrate according to an embodiment of the invention.

Referring to FIG. 6, a pattern having a shape different from the trenchpattern 60 of FIG. 5 may be formed on the substrate 10, which has atleast one element pair consisting of the alloy layer 20 and the materiallayer 30. That is, an etching process may be performed on asemiconductor structure comprising the substrate 10, on which alloylayers 33, 36, 39 and material layers 13, 16, 19 are alternatelystacked, thereby forming a bar pattern designated by the referencenumeral 65. The etching process is preferably performed by using a dryetching technique. The etching process results in exposing therespective sectional surfaces of the alloy layers 33, 36, 39 on the topof the substrate 10, as seen in FIG. 6.

In accordance with this invention, a post-cleaning process may beperformed on the structure as shown in FIG. 6 to remove by-products suchas organic particles and polymer from the substrate having the barpattern 65. The post-cleaning process is performed in accordance withthis invention by using an aqueous solution consisting essentially ofammonium hydroxide (NH₄OH), hydrogen peroxide (H₂O₂), and deionizedwater (DI-water). Hereafter, such an aqueous solution consistingessentially of ammonium hydroxide, hydrogen peroxide and deionizedwater, will be generally referred to as an aqueous solution APM.

FIGS. 7 and 8 are graphs showing etching ratios of aqueous solutionscontaining different proportions of ammonium hydroxide, hydrogenperoxide, and DI-water respectively.

Referring to FIG. 7, substrates having polysilicon layers and substrateshaving alloy layers were prepared. The alloy layers were formed ofsilicon-germanium (Si_(1−x)Ge_(x)) layers which differ from each otherin having different atomic weight percents of germanium atoms withrespect to silicon atoms, respectively. More particularly, the alloylayers used in this example were a Si_(0.8)Ge_(0.2) layer and aSi_(0.7)Ge_(0.3) layer. The polysilicon layer was an undoped layer.

The polysilicon layer and the alloy layers were etched using aqueoussolution APMs, respectively. The etching ratios of aqueous solution APMson a polysilicon layer and an alloy layer, respectively, were examined.The aqueous solution APMs act as cleaning solutions, in which ammoniumhydroxide, hydrogen peroxide, and deionized water were mixed indifferent volume ratios, respectively. The ammonium hydroxide in theaqueous solution APMs has a property of etching the polysilicon layer aswell as the alloy layers. The hydrogen peroxide in the APM solutionsdecreases an oxidation speed on silicon atoms in the order of aSi_(0.7)Ge_(0.3) layer, a Si_(0.8)Ge_(0.2) layer, and the polysiliconlayer.

Firstly, each of the five different aqueous solution APMs was applied toeach of the three different substrate/layer combinations to find theetching ratios of the polysilicon layer 70, the first alloy layer(Si_(0.8)Ge_(0.2)) 80 and the second alloy layer (Si_(0.7)Ge_(0.3)) 90,respectively. FIG. 7 shows bar graphs illustrating the effect of each ofthe APM solutions/sample groups A, B, C, A1, B1 respectively on theetching ratios. APM solutions/sample groups A, B, C were used foretching the polysilicon layer 70 and the alloy layers 80, 90 underconditions of a treatment temperature of 65° C. and a treatment time offive minutes. Aqueous solution APMs/sample groups A, B and C use volumeratios of ammonium hydroxide, hydrogen peroxide, and deionized water of1:1:200, 1:1:500, and 1:2:500, respectively.

The etching ratios depend respectively on the volume ratios of thedeionized water in the first to third aqueous solution APMs/samplegroups A, B and C in the case where the volume ratios of ammoniumhydroxide to hydrogen peroxide remain constant (i.e., A and B). That is,the etching ratios decrease as the volume ratio of the deionized waterincreases in the second relative to the first aqueous solution APM. Thisis because the concentration of ammonium hydroxide is more diluted inAPM solution B than in APM solution A, even at the same proportion ofammonium hydroxide to peroxide.

Further, the etching ratios decrease as the volume ratio of the hydrogenperoxide increases in the third relative to the second aqueous solutionAPM. This is because the peroxide is more concentrated in APM solution Cthan in APM solution B, even at the same proportion of the ammoniumhydroxide to the deionized water. This is because the hydrogen peroxideoverly oxidizes the silicon atoms of the polysilicon layer 70 and thealloy layers 80, 90, and because the hydrogen peroxide and the deionizedwater dilute a concentration of the ammonium hydroxide to reduce theetching ratio of the ammonium hydroxide.

Furthermore, since the first to the third aqueous solution APMs show theetching ratios non-uniformly on the polysilicon layer 70 and the alloylayers 80, 90, the first to the third aqueous solution APMs cannot beapplied to a semiconductor structure in which the sectional surface ofthe alloy layer 20 in the trench 60 is exposed, as shown for example inFIG. 5.

In further testing, two additional APM solutions/sample groups A1 and B1were prepared and used for etching the polysilicon layer 70 and thealloy layers 80, 90 under conditions of a treatment temperature of 50°C. and a treatment time of five minutes, respectively. The fourth andthe fifth aqueous solution APMs/sample groups A1 and B1 have volumeratios of ammonium hydroxide, hydrogen peroxide, and deionized water of1:1:200 and 1:1:500, respectively. The fourth and the fifth aqueoussolution APMs/sample groups were found to have etching ratios smallerthan those of the first to the third aqueous solution APMs/sample groupsA, B and C as discussed above.

Even though the treatment temperature used for the first to the thirdaqueous solution APMs was different than the temperature used for thefourth and fifth APMs, the fourth and the fifth aqueous solution APMsdemonstrate comparable etching ratios relative to the first and secondAPMs as the third aqueous solution APM where both the volume ratio ofthe deionized water and the peroxide concentration were increased. Thisis because a concentration of the ammonium hydroxide is diluted by thedeionized water.

However, since the fourth and the fifth aqueous solution APMs shows theetching ratios non-uniformly on the polysilicon layer 70 and the alloylayers 80, 90, the fourth and the fifth aqueous solution APMs alsocannot be used for treating a structure in which the sectional surfaceof the alloy layer 20 inside the trench 60 is exposed, as shown forexample in FIG. 5.

In view of the results illustrated in FIG. 7, it is seen that aqueoussolution APMs can be formulated and/or utilized so as to beneficiallydecrease the etching ratio of the ammonium hydroxide either byincreasing the volume ratio of the deionized water relative to theammonium hydroxide, by increasing the concentration of the hydrogenperoxide relative to the ammonium hydroxide, and/or by reducing thetreatment temperature. This is because the increase of the volume ratioof the hydrogen peroxide in the third aqueous solution APM oxidizes thepolysilicon layer 70 and the alloy layers 80, 90 very fast, therebylengthening the treatment time.

Further, the reduction of the treatment temperature decreases theactivation energy of the atoms of the ammonium hydroxide, thereby alsodecreasing the etching ratio, as shown in connection with the fourth andthe fifth aqueous solution APMs. Therefore, aqueous solutions comparableto the first to fifth aqueous solution APMs show a possibility for beingapplied to the trench 60 as shown in FIG. 5, but only if combined withone or more of the steps of properly controlling the volume ratios ofthe ammonium hydroxide, the hydrogen peroxide and the deionized water;limiting the treatment time; and/or lowering the treatment temperature.

Referring to FIG. 8, sixth and seventh aqueous solution APMs havingdifferent volume ratios of ammonium hydroxide, hydrogen peroxide, anddeionized water (in contrast to the APMs tested in FIG. 7), are preparedand applied to an alloy layer (Si_(0.7)Ge_(0.3)) 100 and a polysiliconlayer 110. The results of applying the sixth and the seventh aqueoussolution APMs are illustrated in the bar graphs of the two groups D andE in FIG. 8, respectively. Firstly, group D of the two groupsrepresented in FIG. 8 is based on etching the alloy layer 100 and thepolysilicon layer 110 using the sixth aqueous solution APM, which wasprepared with volume ratios of the ammonium hydroxide, the hydrogenperoxide, and the deionized water of 1:1:1000, under conditions of atreatment temperature of 50° C. and a treatment time of ten minutes.Thus, the volume ratio of the deionized water of the sixth aqueoussolution APM is two times the volume ratio of the deionized water usedin the fifth aqueous solution APM (group B1 of FIG. 7). The sixthaqueous solution APM results in substantially the same etching ratios onthe alloy layer 100 and the polysilicon layer 110, which contrasts withthe results seen with group B1. This is because a concentration of theammonium hydroxide in the sixth aqueous solution APM is more dilutedthan that used to produce the group B1 results. Since the sixth aqueoussolution APM shows substantially the same etching ratios on the alloylayer 100 and the polysilicon layer 110, it can be used to treat astructure in which a sectional surface of the alloy layer 20 inside thetrench 60 is exposed, for example as shown in FIG. 5.

Next, group E of the two groups represented in FIG. 8 is based onetching the alloy layer 100 and the polysilicon layer 110 using theseventh aqueous solution APM, which was prepared with volume ratios ofthe ammonium hydroxide, the hydrogen peroxide, and the deionized waterof 1:2:40, under conditions of a treatment temperature of 70° C. and atreatment time of ten minutes. Testing of this seventh aqueous solutionAPM is intended to show a resulting change of an etching ratio inaccordance with the treatment temperature and the treatment time byreducing the volume ratio of the deionized water as compared with thethird aqueous solution APM (group C of FIG. 7). As seen in FIG. 8, usingthe seventh aqueous solution APM increases the etching ratio of thealloy layer 100 significantly compared with the polysilicon layer 110 byreducing the volume ratio of deionized water along with increasing thetreatment temperature and the treatment time. However, since the seventhaqueous solution APM shows significantly different etching ratios forthe alloy layer 100 and the polysilicon layer 110, it may not be used totreat a structure in which a sectional surface of the alloy layer 20inside the trench 60 is exposed, for example as shown in FIG. 5.

Based on the comparative test data, as illustrated in FIGS. 7 and 8, ithas been demonstrated that the volume ratios of the deionized wateralong with the ammonium hydroxide and the hydrogen peroxide can beproperly varied and controlled to form an aqueous solution APM suitablefor applying to the structure of FIG. 5. That is, it has been shown thatthe fourth and the fifth aqueous solution APMs, which have the volumeratios of the ammonium hydroxide, the hydrogen peroxide, and thedeionized water in the range of 1:1:200˜500, if applied at a treatmenttemperature of about 50° C., may be suitable for treating a structure inwhich a sectional surface of the alloy layer 20 inside the trench 60 isexposed, for example as shown in FIG. 5.

Further, the foregoing results show that if the volume ratio of thedeionized water is set as 200, the treatment time using the fourth orthe fifth aqueous solution APM must not exceed about five minutes forsufficiently removing the organic particles and polymeric by-productsfrom the fabricated structure. This is because the etching amount of thealloy layers, e.g., 80, 90, compared with etching of the polysiliconlayer, e.g., 70, increases as the treatment time increases. Therefore,in the case that the volume ratios of the ammonium hydroxide and thehydrogen peroxide is 1:1, the volume ratio of deionized water shouldpreferably be in the range of 300˜500.

Furthermore, the sixth aqueous solution APM (group D of FIG. 8) showedsubstantially the same etching ratio on the alloy layer 100 and thepolysilicon layer 110 by using an APM solution having volume ratios ofthe ammonium hydroxide, the hydrogen peroxide, and the deionized waterof 1:1:1000. Based on these results, it can be seen that improvedresults are realized if the volume ratio of the ammonium hydroxide inthe fourth or the fifth aqueous solution APM of FIG. 7 is set as 1, thevolume ratio of the hydrogen peroxide to the deionized water isestablished in the range of about 0.5˜20:300˜2000. Thus, the volumeratios of the ammonium hydroxide, the hydrogen peroxide, and thedeionized water can be selected, for example as 1:0.5:300, in order toreduce the etching ratio of the ammonium hydroxide on the alloy(Si_(1−x)Ge_(x)) layer, by minimizing the oxidation of the alloy(Si_(1−x)Ge_(x)) layer and increasing the relative volume ratio ofdeionized water. On the other hand, the volume ratios of the ammoniumhydroxide, the hydrogen peroxide, and the deionized water can beselected, for example as 1:20:2000, in order to reduce the etching ratioof ammonium hydroxide by increasing the volume ratio of the hydrogenperoxide within an allowable range suitable for the post-cleaningprocess to maximize an oxidation speed of the alloy (Si_(1−x)Ge_(x))layer and maximize the volume ratio of the deionized water.

Hereafter, aqueous solution APMs, for example the fourth and the fifthaqueous solution APMs discussed above, having volume ratios of theammonium hydroxide, the hydrogen peroxide, and the deionized water inthe range of about 1:0.5˜20:300˜2000 will be referred to as “an aqueoussolution diluted ammonia and peroxide mixture (APM).” In accordance withthis invention, an aqueous solution diluted APM has been found tofunction well as a cleaning solution usable at treatment temperatures ofabout 50 to 70° C. Further, an aqueous solution diluted APM may be alsoused in some invention embodiments at a treatment temperature eitherbelow 50° C. or above 70° C.

FIGS. 9 through 14 are schematic cross-sectional views of portions ofsemiconductor devices treated by using various aqueous solutionsconsisting essentially of ammonium hydroxide and hydrogen peroxide,respectively. The various aqueous APM solutions used to treat thesemiconductor structures have different volume ratios of the ammoniumhydroxide, the hydrogen peroxide, and the deionized water, respectively.The various aqueous APM solutions are used in a plurality ofpost-cleaning processes, respectively, as described below.

Referring to FIGS. 9 and 10, a post-cleaning process (represented by thearrows 120) is performed on the fabricated substrate structure havingthe trench 60 as shown in FIG. 5. In one embodiment, the post-cleaningprocess 120 is performed using an eighth aqueous solution APM havingvolume ratios of ammonium hydroxide, hydrogen peroxide, and deionizedwater of 1:4:20 at a temperature of 70° C. for ten minutes. The alloylayer 20 shown in FIG. 9 is formed of a silicon-germanium(Si_(1−x)Ge_(x)) layer, and the material layer 30 is formed of astrained silicon layer.

The eighth aqueous solution APM is applied to the side portions of alloylayer 20 and material layer 30 exposed along the trench 60 to removeorganic particles and polymeric by-products that may remain on thesidewall and the bottom of the trench 60 after fabrication operations.The eighth aqueous solution APM partially removes portions of the alloylayer 20 adjacent to trench 60 such that the sectional surface thereofis no longer substantially in alignment with the sectional surfaces ofthe material layer 30 and the substrate 10, as shown in FIG. 9. As such,treatment with the eighth aqueous solution APM forms small grooves 135on either side of the trench 60. FIG. 10 shows an enlarged view of aportion 130 (see FIG. 9) of the trench 60 by using VSEM analysis. Theformation of grooves 135 limits the application of the post-cleaningprocess 120 performed in the trench 60. Therefore, it is not normallyacceptable to use a cleaning solution similar to the eighth aqueoussolution APM on the substrate having the trench 60 as shown in FIG. 9.Such an aqueous solution APM might be modified in composition, however,or the treatment step might be modified relative to temperature andtime, in the ways discussed above, for example, to reduce or minimizethe formation of grooves 135 during a post-cleaning process.

Referring to FIGS. 11 and 12, a post-cleaning process (represented bythe arrows 120) is performed on the fabricated substrate structurehaving the bar pattern 65 as shown in FIG. 6. The bar pattern 65 isformed to have the material layers 13, 16, 19 and the alloy layers 33,36, 39 alternately stacked. In one embodiment, the post-treatmentprocess 120 is performed using the same eighth aqueous solution APM withthe same conditions (treatment temperature, treatment time) as discussedabove in connection with FIG. 9. The alloy layers 33, 36, 39 are formedof silicon-germanium (Si_(1−x)Ge_(x)) layers, respectively, and thematerial layers 13, 16,19 are formed of strained silicon layers,respectively.

The eighth aqueous solution APM is applied to the upper surface of toplayer 19 and to the respective exposed side portions of the alloy layers33, 36, 39 and the material layers 13, 16, 19 to remove organicparticles and the polymeric by-products that may remain on the sidewallsof the bar pattern 65 and on the upper surface of the substrate 10 afterfabrication operations. The eighth aqueous solution APM partiallyremoves side portions of the alloy layers 33, 36, 39 such that thesectional surfaces thereof are no longer in alignment with the sectionalsurfaces of the material layers 13, 16, 19, as shown in FIG. 11. Assuch, treatment with the eighth aqueous solution APM forms small grooves145 on either side of the bar pattern 65. FIG. 12 shows an enlarged viewof a portion 140 (see FIG. 11) of the bar pattern 65 by using VSEManalysis. The formation of grooves 145 limits the application of thepost-cleaning process 120. The post-cleaning process 120 can also leadto droplets of the APM solution running down the bar pattern 65 onto thesubstrate 10 causing an electrical short with adjacent patterns on thesubstrate. Therefore, it is not normally acceptable to use a cleaningsolution similar to the eighth aqueous solution APM on the substratehaving the bar pattern 65. Such an aqueous solution APM might bemodified in composition, however, or the treatment step might bemodified relative to temperature and time, in the ways discussed above,for example, to reduce or minimize the formation of grooves 145 during apost-cleaning process.

Referring to FIGS. 13 and 14, a different post-cleaning process(represented by the arrows 150) is performed on the fabricated substratestructure having the trench 60 as shown in FIG. 5. In one embodiment,this alternative post-cleaning process 150 is performed using an aqueoussolution diluted APM having volume ratios of the ammonium hydroxide, thehydrogen peroxide, and the deionized water of 1:1:1000 at a temperatureof 50° C. for ten minutes. The alloy layer 20 and the material layer 30are formed comparable to that shown in FIG. 9.

The aqueous solution diluted APM is applied to the side portions ofalloy layer 20 and material layer 30 exposed along the trench 60 toremove organic particles and polymeric by-products that may remain onthe sidewall and the bottom of the trench 60 after fabricationoperations. The aqueous solution diluted APM does not excessively etchthe side wall portions of alloy layer 20 exposed along the trench 60.This is because the etching ratios of the ammonium hydroxide on the sidewall portions of material layer 30 and the side wall portions of alloylayer 20 are substantially identical. The ammonium hydroxideconcentration in this diluted APM solution is lower because it is morediluted by the deionized water. FIG. 14 shows an enlarged view of aportion 152 (see FIG. 13) of the trench 60 by using VSEM analysis. Theaqueous solution diluted APM therefore does not limit the application ofthe alternative post-cleaning process 150. Accordingly, it is preferableto use the aqueous solution diluted APM on the substrate having thetrench 60 as shown in FIG. 13. Correspondingly, the alternativepost-cleaning process 150 may also have application to the substratehaving the bar pattern 65 of FIG. 11 by using the aqueous solutiondiluted APM.

Furthermore, the aqueous solution diluted APM may be also used toperform a wet etching process on the trench 60 in FIG. 13, which may beplasma-damaged after the dry etching process. In this application, theaqueous solution diluted APM etches the sidewall and the bottom of thetrench 60 to remove plasma-damaged layers, while applying substantiallythe same etching ratio to both the material layer 30 and the alloy layer20. Such a wet etching process is typically performed for a longer timethan the post-cleaning process 150.

A post-cleaning process such as process 150 may be performed by using acleaning apparatus of a spin type, a spin spray type or a dipping type.A cleaning apparatus of the spin type is preferably used by employing atleast one element selected from the apparatus element group consistingof a brush, a di-sonic device, an ultra-sonic device, and a mega-sonicdevice. A cleaning apparatus of the spin spray type may be used byemploying at least one element selected from the apparatus element groupconsisting of a brush, a di-sonic device, an ultra-sonic device, and amega-sonic device. A cleaning apparatus of the dipping type may be usedby employing at least one element selected from the apparatus elementgroup consisting of a brush, a di-sonic device, an ultra-sonic device,and a mega-sonic device.

FIG. 15 is a schematic cross-sectional view of a portion of asemiconductor device having an alloy layer according to an embodiment ofthe invention, and FIG. 16 is a related graph comparing surfaceroughnesses of alloy layers treated by using various aqueous solutionsconsisting essentially of ammonium hydroxide and hydrogen peroxide.

Referring to FIG. 15, at least one growth process (represented by thesingle arrow 160 or, alternatively, by arrows 163 and 166) is performedon a substrate 10 to form an alloy (Si_(1−x)Ge_(x)) layer 20. Thesilicon-germanium alloy layer 20 is formed such that germanium atoms arepresent in alloy layer 20 in the range of greater than 0 to about 99% byatomic weight with respect to the presence of silicon atoms. Thesubstrate 10 is ordinarily preferably formed of a single crystallinesilicon, but in some invention embodiments the substrate 10 may insteadbe formed of a polycrystalline silicon. The growth process(es) to formthe layer 20 on the substrate 10 may be performed, for example, by achemical vapor deposition (CVD) process. In the case of using one growthprocess 160, the alloy layer 20 is formed to have a rough upper surfaceS1 with a predetermined thickness T. Further, in the case of using twosequential growth processes 163, 166, the alloy layer 20 is formed tohave different rough surfaces (upper surface S1 and intermediate surfaceS2) with a predetermined total thickness T (where S2 is an intermediatesurface on which additional alloy layer is formed or deposited by growthprocess 166 to complete the formation of layer 20).

The alloy layer 20 having the predetermined thickness T and the roughupper surface S1 may be formed, for example, by exposing a surface ofsubstrate 10 to the atmosphere from a CVD apparatus in order to performone growth process 160. Alternatively, the alloy layer 20 having apredetermined thickness T, the rough upper surface S1, and the roughintermediate surface S2, may be formed, for example, by exposing asurface of substrate 10 to the atmosphere from a CVD apparatus two timesin order to perform two sequential growth processes 163, 166. Followingformation of all or a portion of alloy layer 20, a chemical mechanicalpolishing process and a cleaning process (both represented by the arrows170) may be sequentially performed to smooth the rough upper surface S1,or on each of the rough surfaces, such as on upper surface S1 and onintermediate surface S2, of the alloy layer 20 after each time thesubstrate 10 is exposed to atmosphere from the CVD apparatus. Thechemical mechanical polishing process planarizes the rough surface S1,or each of the rough surfaces S1, S2, of the alloy layer 20, andmitigates the surface roughness. The cleaning process removes theparticles generated from the chemical mechanical polishing process, andpartially etches the upper surface S1, or each of the upper surface S1,and the intermediate surface S2, of the alloy layer 20, thereby tofurther mitigate the surface roughness.

The cleaning process may be performed by using a cleaning apparatus of aspin type, a spin spray type or a dipping type. A cleaning apparatus ofthe spin type is preferably used by employing at least one elementselected from the apparatus element group consisting of a brush, adi-sonic device, an ultra-sonic device, and a mega-sonic device. Acleaning apparatus of the spin spray type may be used by employing atleast one element selected from the apparatus element group consistingof a brush, a di-sonic device, an ultra-sonic device, and a mega-sonicdevice. A cleaning apparatus of the dipping type may be used byemploying at least one element selected from the apparatus element groupconsisting of a brush, a di-sonic device, an ultra-sonic device, and amega-sonic device.

The cleaning process used at this stage of semiconductor manufacture isgenerally known to use a basic organic aqueous solution which includesan effective amount of hydrofluoric acid (HF), ammonium hydroxide(NH₄OH) or acetic acid (CH₃COOH). The basic organic aqueous solution mayalso include an effective amount of hydrogen peroxide (H₂O₂), whereinthe hydrogen peroxide serves to oxidize the alloy layer 20 to acceleratean etching ratio of the hydrofluoric acid, ammonium hydroxide, or aceticacid component. However, the hydrogen peroxide may etch the surface ofthe alloy layer 20 non-uniformly while performing this cleaning process.To cope with this situation, an aqueous solution diluted APM inaccordance with this invention can instead be applied to the alloy layer20 on substrate 10 as shown in FIG. 15 to mitigate the surface roughnessof the alloy layer 20.

Alternately, an aqueous solution diluted APM in accordance with thisinvention may be applied to a structure having an exposed portion ofsubstrate 10 as shown in FIG. 13 to mitigate the surface roughnessthereof. This treatment procedure can also be applied to a singlecrystalline silicon substrate which does not have an alloy layer or amaterial layer on the top thereof.

Referring to FIG. 16, a graph is provided to illustrate theeffectiveness in mitigating a surface roughness of a single crystallinesilicon substrate by using either an aqueous solution APM selected fromthe first to seventh aqueous solution APMs discussed previously, or anaqueous solution diluted APM as also discussed previously. In the graph,four groups of samples, F, G, H, and I are represented. Two groups, Fand G, of the four groups exhibited surface roughness values of a singlecrystalline silicon substrate using an atomic force microscope (AFM).One group, F, was not treated with an aqueous solution APM or with anaqueous solution diluted APM, while the other group, G, was treated withan aqueous solution APM having volume ratios of ammonium hydroxide,hydrogen peroxide, and deionized water of 1:1:500 at a treatmenttemperature of 50° C. Two groups H and I, of the four groups exhibitedsurface roughness values of a single crystalline silicon substrate. Onegroup, H, was treated with an aqueous solution APM having volume ratiosof ammonium hydroxide, hydrogen peroxide, and deionized water of 1:1:500at a treatment temperature of 60° C., while the other group, I, of thesetwo groups was treated with an aqueous solution diluted APM having avolume ratio of ammonium hydroxide, hydrogen peroxide, and deionizedwater of 1:1:1000 at a treatment temperature of 50° C. For each of thegroups F, G, H, and I, the surface roughness values were checked on acentral surface portion 180 and on a peripheral surface portion 190 ofeach single crystalline silicon substrate, respectively.

The results show that the surface treated with the aqueous solutiondiluted APM exhibits surface roughness values similar to those of thesamples treated with different aqueous solution APMs (having differentvolume ratios of ammonium hydroxide, hydrogen peroxide, and deionizedwater), so that the aqueous solution diluted APM may be effectively usedto perform the cleaning process on the alloy layer 20 of FIG. 15.

As described above, this invention provides a method of performing acleaning process on a semiconductor structure having at least one alloy(Si_(1−x)Ge_(x)) layer by using an aqueous solution diluted APM toalways maintain a substantially aligned profile of the layered structureand to mitigate a surface roughness of the at least one alloy(Si_(1−x)Ge_(x)) layer. As such, the aqueous solution diluted APM ofthis invention improves the cleaning process for example by reducing thelimits and restrictions on using aqueous solution APMs and by minimizingor eliminating damage to a treated semiconductor structure.

Embodiments of the invention will now be described in a non-limitingway.

Embodiments of the invention provide methods of fabricating asemiconductor device by using a diluted aqueous solution of ammonia andperoxide mixture (APM) as defined herein.

According to some embodiment of the invention, there are providedmethods of fabricating a semiconductor device by using an aqueoussolution diluted APM that include forming an alloy layer on a substratethrough at least one growth process. A cleaning process is thenperformed on the alloy layer using an aqueous solution diluted ammoniaand peroxide mixture (APM). Volume ratios of ammonium hydroxide (NH₄OH),hydrogen peroxide (H₂O₂), and deionized water (DI-water) in the aqueoussolution diluted APM are preferably in the range of about1:0.5˜20:300˜2000, respectively.

According to other embodiments of the invention, there are providedmethods of fabricating a semiconductor device by using an aqueoussolution diluted APM that include sequentially forming at least one pairof an alloy layer and a different material layer on a substrate. A dryetching process is performed in the material layer and the alloy layerto expose sectional surfaces of the material layer and the alloy layerwhich are formed on top of the substrate. A cleaning process is thenperformed on the substrate structure having the sectional surfaces ofthe material layer and the alloy layer using an aqueous solution dilutedAPM wherein the volume ratios of ammonium hydroxide (NH₄OH), hydrogenperoxide (H₂O₂), and deionized water (DI-water) in the aqueous solutiondiluted APM are preferably in the range of about 1:0.5˜20:300˜2000,respectively.

1. A method of fabricating a semiconductor device comprising thesequential steps of: sequentially forming at least one pair of an alloylayer and a different material layer on a substrate; performing a dryetching process in the material layer and the alloy layer to exposesectional surfaces of the material layer and the alloy layer which areformed on top of the substrate; and performing a cleaning process on thesubstrate structure having the sectional surfaces of the material layerand the alloy layer using an aqueous solution diluted APM wherein thevolume ratios of ammonium hydroxide (NH₄OH), hydrogen peroxide (H₂O₂),and deionized water (DI-water) in the aqueous solution diluted APM arein the range of about 1:0.5˜20:300˜2000, respectively.
 2. The methodaccording to claim 1, wherein the different material layer is formed ofa strained silicon layer.
 3. The method according to claim 1, whereinthe different material layer is formed by using an epitaxial process. 4.The method according to claim 1, wherein the alloy layer is asilicon-germanium layer formed of silicon and germanium atoms whereinthe germanium atoms are present in the alloy layer in the range ofgreater than 0 to about 99% by atomic weight with respect to thepresence of silicon atoms.
 5. The method according to claim 1, whereinthe alloy layer is formed by using a chemical vapor deposition process.6. The method according to claim 1, wherein the substrate is formed of asingle crystalline silicon layer.
 7. The method according to claim 1,wherein the substrate is formed of a polycrystalline silicon layer. 8.The method according to claim 1, wherein the cleaning process isperformed by using a cleaning apparatus of a spin type, a spin spraytype or a dipping type of apparatus.
 9. The method according to claim 8,wherein a cleaning apparatus of the spin type is used by employing atleast one element selected from the apparatus element group consistingof a brush, a di-sonic device, an ultra-sonic device, and a mega-sonicdevice.
 10. The method according to claim 8, wherein a cleaningapparatus of the spin spray type is used by employing at least oneelement selected from the apparatus element group consisting of a brush,a di-sonic device, an ultra-sonic device, and a mega-sonic device. 11.The method according to claim 8, wherein a cleaning apparatus of thedipping type is used by employing at least one element selected from theapparatus element group consisting of a brush, a di-sonic device, anultra-sonic device, and a mega-sonic device.
 12. The method according toclaim 1, further comprising a planarization step and a cleaning stepsequentially performed on the alloy layer before forming the materiallayer thereon, in which the planarization step is performed by using achemical mechanical polishing process, and the cleaning step isperformed by using an aqueous solution diluted APM.
 13. The methodaccording to claim 1, wherein the dry etching step exposes the sectionalsurfaces of the material layer and the alloy layer by forming a trenchin the at least one pair of the material layer and the alloy layer. 14.The method according to claim 1, wherein the sectional surfaces of thematerial layer and the alloy layer are exposed by forming a bar patternhaving the at least one pair of the material layer and the alloy layeron the substrate through the dry etching process.
 15. The methodaccording to claim 1, further comprising a wet etching step, afterperforming the cleaning process, wherein the wet etching process iscarried out using an aqueous solution diluted APM to removeplasma-damaged portions of the at least one pair of the material layerand the alloy layer.